After water, protein is the second most abundant component, accounting for about 16% of the protein in an adult ^male2). 2) The next most abundant component is fat (lipid), which accounts for about 15%. In addition to these, the human body contains about 6% minerals, which are also found in rocks and soil.

What are the functions of these ingredients in the body? Let's look at them in order.

First, water that enters the body through the mouth is absorbed by the intestines and then circulates through the body as "body fluid" such as blood. Body fluid carries oxygen and nutrients to all parts of the body, expels unneeded substances from the body, and regulates body temperature.

Protein is the main material for muscles, bones, internal organs, skin, nails, and hair. Protein entering the body is broken down into "amino acids" in the small intestine and absorbed. After that, they become materials for muscles, "hormones" that regulate body functions, "enzymes" that assist chemical reactions in the body, and "antibodies" that protect the body from pathogens.

Although fat is often dismissed as a problem when it increases too much in adulthood, it has important functions just like any other component. First, each gram of fat releases approximately 9 kcal (kilocalories) ³⁾. 3) In addition to protecting the body from cold, fat also serves as a material for hormones and cell membranes, protects the internal organs by becoming subcutaneous fat, and facilitates the absorption of fat-soluble vitamins, which are easily soluble in oil.

There are 114 types of minerals, 16 of which are considered "essential minerals" for the human body, but it is important to note that potassium, calcium, iron, and zinc are easily ^deficient4). For example, a lack of calcium prevents the growth of strong bones and teeth. Iron deficiency is one of the causes of anemia.

All of these nutrients are taken into the body through food. In other words, it is important to eat a well-balanced variety of foods in order to build a healthy body.